Not Appllicable.
1. Field on Invention
The field of the present invention relates generally to wireless telecommunications and, more particularly, to methods and apparatuses for fixing the location of a fixed wireless terminal in a wireless network.
2. Description of Background
Throughout the world, there exist places where conventional landline telephone service is unavailable or inadequate. In addition, it is typically expensive and time-consuming to build a wireline network. In recent years, however, wireless telephone service has proliferated throughout the world, including places that never offered landline service. Wireless service can support many potential customers without the capital expenses associated with digging up streets and wiring older business districts. Installation of a wireless network can be accomplished in a matter of months, rather than the years associated with installing a wireline network. Thus, many locations around the world that do not have an embedded wireline network or have an inadequate wireline network are seeking to implement wireless solutions.
Wireless service, however, is generally more expensive than equivalent wired service. Wireless service providers generally believe that mobile flexibility demands a premium service charge and, unlike a dedicated wireline network, wireless customers share a limited resource-RF spectrum bandwidth. Thus, wireless service providers typically offer usage-sensitive pricing, which has a tendency to control access to the wireless network and limit wasteful use. Wireless service users in locations with no or inadequate landline service, however, perceive that wireless service should be offered at rates competitive to wireline networks.
As a result, some wireless service providers offer fixed wireless solutions in these locations at a discount over mobile wireless service. Offering fixed wireless service at lower rates than mobile wireless service presents the technical dilemma of differentiating between regular mobile wireless users and fixed wireless users. The typical fixed wireless system includes a fixed wireless terminal for interfacing a fixed wireless user""s telephone unit with a mobile switching center (MSC). The fixed wireless terminals are preferably confined to a fixed location, such as mounted to the side of a user""s residence or equipment rooms, basements, attics, and closets, within the geographic area serviced by the fixed wireless network. However, because the fixed wireless terminal is essentially a wireless device, it may simply be removed from its fixed location and thus become a de facto mobile telephone interface.
A variety of solutions have been offered to prevent misuse and abuse of fixed wireless systems. One prior solution has been to offer specific location or home-zoning pricing plans, in which, for example, calls originating from and terminating at a particular cell site are subject to a fixed wireless rate, and calls which do not originate and terminate at the particular site are subject to the mobile rate. Home-zoning plans, however, are difficult to implement, especially in urban areas, where cell configurations may periodically change during periods of high wireless volume. Moreover, such a solution is relatively expensive to implement, in part because the existing billing system would have to be rewritten to support the functionality.
Another suggested solution is to incorporate Global Positioning System (GPS) receivers into fixed wireless terminals to generate accurate readings with respect to the physical location of a user. That solution, however, would require that the hardware and software supporting the GPS system be installed in all terminals, and thus would likely increase the cost of the terminal.
Another prior solution involves installing a motion detector, such as a mercury switch, in the fixed wireless unit. The motion detector is in communication with a controller for the fixed wireless unit, and instructs the controller to disable the unit when motion is detected. Such a system, however, is susceptible to tampering or sabotage which may render the motion detector nonfunctional.
Many other attempts have been made at restricting or controlling access or determining location of a wireless terminal. For example, it is known to restrict call setup by defining a fixed subscription area (FSA) in the mobile switching center (MSC). Any attempts by the subscriber terminal to access the system will be denied or redirected to accesses within the FSA. This prohibits significant movement of the fixed subscriber, but allows normal subscriber access within, near, or slightly outside of the cell coverage area of the FSA. The major disadvantage with this system is that extensive changes are required in the MSC operating software.
In addition, a method specifically designed to support TDMA wireless fixed operation is known which involves changes to the MSC operating software by defining a location area identity (LAI), not unlike the FSA previously described. The switch maintains a list of handover candidates for the fixed wireless terminal. Any time the terminal moves beyond the fixed area, a handover is attempted to one of the handover candidates. Further, a timing advance (TA) value is maintained for each cell in the candidate list. This TA value is essentially a compensation value for the round trip time of a signal from the base station to the wireless terminal. If the TA value for the home cell or any handover candidate cell is out of range of the stored value, a violation signal is sent to the system operator. Further call termination is possible.
Other more complex and accurate solutions have been developed. For instance, it is known to determine the location of a wireless terminal by measuring the relative time of arrival of a single data packet transmitted by each of three independent transmitting antennas. Because the locations of the antennas are known, the receiver can compute its own location. Again, however, such a method requires extensive system changes to support the transmission of the data packets by three base stations or, at the very least, three spatially diverse antenna locations.
According to another known method of determining the position of a subscriber terminal, a mobile unit utilizing a plurality of range transceivers located at known fixed locations are adapted to transmit approximately synchronized digital range signals. This system appears to mimic the functionality of the global GPS system, although implemented with frequencies assigned to the wireless provider.
The above-described solutions, though all plausible for location determination, are not entirely suitable for a simple fixed wireless device location fixer. They all require extensive system modifications. They all require extensive changes to the MSC operating software or to some ancillary devices. Another disadvantage of the latter two solutions is they not only require extensive system development, but they also require frequency spectrum, a quite valuable commodity.
Therefore, there exists a need for a method and apparatus to fix the location of a fixed wireless terminal which eliminates the need for additional hardware and installation expenses. There also exists a need for a method and apparatus to fix the location of a fixed wireless terminal which would reduce the likelihood tampering, sabotage, and fraud.
The present invention provides a practical implementation for fixing the location of a fixed wireless terminal based on telecommunication signals, such as signals received from base stations of a fixed wireless network. The signals are received on one or more channels and are used to construct models of the network environment of the fixed wireless terminal at different times, such as periodically or each time the terminal is used. The most recent model is compared to one or more previous models to determine if the fixed wireless terminal has changed locations, i.e., if it is mobile. The models may be constructed from one or more features of the received signals.
According to one embodiment of the present invention, the network environment models are constructed from identification codes sent with each of the signals. The identification codes are typically transmitted with telecommunication signals in a mobile telecommunications network to ensure that a mobile telecommunications device is communicating with the proper base station. For example, in a digital network, a digital verification color code (DVCC) is typically sent with all signals on digital control channels. According to another embodiment, models are constructed from digital color codes and their corresponding analog control channel or supervisory audio tones and their corresponding analog voice channel.
According to another embodiment, the present invention generates network environment models based on the strength of the received telecommunications signals. In addition, the models may include the signal strength of the received signals on certain channels in conjunction with the identification codes for those channels. According to yet another embodiment, the present invention monitors a time of arrival of signals received from different base stations to generate the network environment models.
If the most recent model and a previous model of the network environment sufficiently match, the present invention assumes that the location of the fixed wireless terminal has not changed. Conversely, if the models do not sufficiently match, the present invention assumes that the location of the fixed wireless terminal has changed and that, therefore, the fixed wireless terminal is mobile. If the fixed wireless terminal is mobile, the present invention may prevent a user from accessing the network via the fixed wireless terminal for a period of time, such as twenty-four hours. To ameliorate such potentially harsh ramifications, the present invention may be programmed to only prevent access to the network if the fixed wireless terminal is determined to be mobile on a specified number of occasions within a certain time period. Moreover, the present invention may be programmed to nevertheless permit access to the network for identifiable emergency purposes even if access would be otherwise prevented.
Thus, the present invention fixes the location of a fixed wireless terminal and prevents its use as a de facto mobile telecommunications device without the expensive additional hardware. In addition, the present invention represents an advancement over the prior art because it is not readily susceptible to tampering, fraud, or sabotage. These and other benefits of the present invention will be apparent from the detailed description of the invention hereinbelow.